This invention relates generally to communication systems and, more particularly, to determining whether a reading from a pressure transducer is valid.
Powered systems such as, but not limited to, an off-highway vehicle, marine powered propulsion plant or marine vessel, rail vehicle systems or trains, stationary power plants, agricultural vehicles, and transport vehicles, usually are powered by a power unit, such as but not limited to a engine, such as but not limited to a diesel engine. With respect to rail vehicle systems, the powered system is a locomotive, which may be part of a train that further includes a plurality of rail cars, such as freight cars. Usually more than one locomotive is provided as part of the train, where a grouping of locomotives is referred to as a locomotive “consist.” Locomotives are complex systems with numerous subsystems, with each subsystem being interdependent on other subsystems.
With respect to a train, under operator control, a railroad locomotive supplies motive power (traction) to move the locomotive and a load (e.g., non-powered railcars and their contents), and applies brakes on the locomotive and/or on the non-powered railcars to slow or stop the train. With respect to the locomotive, the motive power is supplied by electric traction motors responsive to an AC or DC power signal generated by the locomotive engine.
A railroad train has three separate brake systems. An air brake system includes a fluid-carrying (typically the fluid includes air) brake pipe that extends a length of the train and a railcar brake system. Wheel brakes are applied or released at each locomotive and at each railcar in response to a fluid pressure in the brake pipe. An operator-controlled brake handle controls the brake pipe pressure, venting the brake pipe to reduce the pressure to signal the locomotives and railcars to apply the brakes, or charging the brake pipe to increase the pressure to signal the locomotive and railcars to release the brakes. For safe train operation, when pressure in the brake pipe falls below a threshold value the brakes default to an applied condition.
Each locomotive also has an independent pneumatic brake system controlled by the operator to apply or release the locomotive brakes. The independent pneumatic brake system, which is coupled to the air brake system, applies the locomotive brakes by increasing the pressure in the locomotive brake cylinders and releasing the locomotive brakes responsive to a decrease in the cylinder air pressure.
Finally, each locomotive is equipped with a dynamic brake system. Activation of the dynamic brakes reconfigures the locomotive's traction motors to operate as generators, with the inertia of the locomotive wheels supplying rotational energy to turn the generator rotor winding. Magnetic forces, developed by generator action, resist wheel rotation and thus create wheel-braking forces. The energy produced by the generator is dissipated as heat in a resistor grid in the locomotive and removed by one or more cooling blowers. Use of the dynamic brakes is indicated to slow the train when application of the locomotive independent brakes and/or the railcar air brakes may cause the locomotive or railcar wheels to overheat or when prolonged use may cause excessive wheel wear. For example, the dynamic brakes may be applied when the train is traversing a prolonged downgrade.
A train configured for distributed power (DP) operation has a lead locomotive at a head-end of the train, and one or more remote locomotives between the head-end and an end of the train. A DP train may also include one or more locomotives at the end of the train. The DP system further includes a distributed power train control and communications system with a communications channel (e.g., a radio frequency (RF) or a wire-based communications channel) linking the lead and remote locomotives. Though DP operation is disclosed specific to trains, similar systems are also applicable for other powered systems disclosed herein.
The DP system generates traction and brake commands responsive to operator-initiated (e.g., the operator in the lead locomotive) control of a lead locomotive traction controller (or throttle handle) or a lead locomotive brake controller (responsive to operation of an air brake handle, a dynamic brake handle or an independent brake handle). These traction or brake commands are transmitted to the remote locomotives over the DP communications channel. The receiving remote locomotives respond to the traction or brake (apply and release) commands to apply tractive effort or to apply/release the brakes and further advise the lead locomotive that the command was received and executed. For example, when the lead locomotive operator operates the lead-locomotive throttle controller to apply tractive effort at the lead locomotive, according to a selected throttle notch number, the DP system issues commands to each remote locomotive to apply the same tractive effort (e.g., the same notch number). Each remote locomotive replies to acknowledge execution of the command.
In certain DP systems, a plurality of pressure transducers are used in an equalizing/control reservoir, brake pipe, brake cylinder, etc. at the lead locomotive and at each remote locomotives to sense when the lead locomotive makes a brake application and allows each remote locomotive to make a similar brake application. This allows for uniform braking to take place, which in turn keeps in-train forces at acceptable limits.
FIG. 1 schematically illustrates an exemplary distributed power train 10, traveling in a direction indicated by an arrowhead 11. A remote locomotive 12A (also referred to as a remote unit) is controlled by messages transmitted from either a lead locomotive 14 (also referred to as a lead locomotive) or from a control tower 16. Control tower commands are issued by a tower operator or dispatcher either directly to the remote locomotive 12A or to the remote locomotive 12A via the lead locomotive 14.
A trailing locomotive 15 coupled to the lead locomotive 14, forming a consist, is controlled by the lead locomotive 14 via control signals carried on an MU (multiple locomotive) line 17 connecting the two units. Also, a trailing remote locomotive 12B coupled to the remote locomotive 12A, forming another consist, is controlled by the remote locomotive 12A via control signals carried on the MU line 17.
Each of the locomotives 14 and 12A and the control tower 16 includes a DP transceiver 28L, 28R, 28T (also referred to as a DP radio) and a DP antenna 29 for receiving and transmitting the DP communication messages. The DP transceivers are referred to by suffixed reference numerals 28L, 28R and 28T indicating location in the lead locomotive, remote locomotive, and the control tower, respectively.
The DP commands are typically generated in a lead station 30L in the lead unit 14 responsive to operator control of the motive power and braking controls in the lead locomotive 14, as described above. The remote locomotive 12A also includes a remote station 32R for processing messages from the lead locomotive 14 and for issuing reply messages and commands.
The distributed power train 10 further comprises a plurality of railcars 20 interposed between the locomotives illustrated in FIG. 1 and connected to a brake pipe 22. The railcars 20 are provided with an air brake system (certain components of which are not shown in FIG. 1) that applies the railcar air brakes in response to a pressure drop in the brake pipe 22 and releases the air brakes in response to a pressure increase in the brake pipe 22. The brake pipe 22 runs the length of the train for conveying the air pressure changes specified by air brake controllers 24 in the locomotives 14 and 12A. A plurality of transducers 69 is provided. The plurality of transducers 69 are associated with the equalizing/control reservoir, brake pipe, and brake cylinder at each brake controller 24 at each lead and remote locomotive. The transducers 69 communicate with the lead station 30L in the lead locomotive 14 to identify the brake application that the driver is commanding at the lead locomotive. The lead station then transmits this brake application data to the remote station 32R via the DP radios 28L and 28R. The remote station 32R then commands the remote brake controllers 24 to apply brakes as commanded from the lead locomotive. The transducers 69 communicate with the remote station 32R in the remote locomotive 12A to identify that the remote locomotive 12A is making its braking application in response to the braking application made by the lead locomotive 14.
In distributed power applications, it is especially critical to have valid and accurate pressure transducer data. During times of communication interruption, if a brake application is applied at the lead locomotive, the remote locomotive cannot receive this brake command and the lead locomotive may apply brakes at the front part of the train very rapidly while the rear part of the train the brakes are being applied at a much slower rate. Such an application of brakes may result in experiencing high in-train forces, which are unacceptable during train motoring. Additionally, pressure transducers may fail at an acceptable pressure and provide a false reading to the lead locomotive, or, more specifically, a train control system. This false reading will indicate to the system that it is safe to operate in a nominal state. The false reading might allow the system to make an unacceptable action.
Therefore, owners and operators of locomotives and trains would benefit from being able to detect when a failed or stuck pressure transducer is realized where the detection ensures that the data associated with the detection is current data. Owners and operators would also benefit from having fewer working parts in the distributed power system; therefore, an additional benefit would be realized if the detection is accurate enough to reduce the number of redundant transducers currently required.